In recent years, great progress has been made in the bioengineering field, particularly, tissue engineering for treating and regenerating tissues. Tissue engineering is an interdisciplinary field that applies the principles of cytology, life sciences, engineering and medical science toward the development of biological substitutes that restore, maintain or improve tissue function or a whole organ, based on the understanding of relationship between structures and functions of tissues. In other words, tissue engineering aims to maintain, enhance or restore functions of the body, using implantable, artificial bio-tissues. In this regard, tissue engineering is directed to the study of stem cell proliferation and differentiation, the decelopment of cyto- or biocompatible three-dimensional scaffolds, and the development of various tissue engineering tools. Of them, the three-dimensional scaffold for supporting stem cells or histocytes is an essential element in developing artificial tissues and organs.
Major requirements of scaffold materials for use in tissue regeneration are as follows. First, they should play a fully sufficient role as a substrate or frame where histocytes of interest are allowed to well adhere thereto and driven to form a tissue of desired three-dimension. Also, they should function as an intermediate barrier between implant cells and host cells. Accordingly, scaffold materials should be non-toxic and bio-compatible sufficiently not to incur blood coagulation or inflammation after transplantation. Another factor is biodegradability. Scaffold materials should be completely degraded in vivo with time after the implanted cells have been guided to perform full functions and roles as tissues. Hence, a scaffold is three-dimensionally fabricated mostly of a synthetic or natural polymer, or a composite thereof, with various morphologies and properties given thereto. Predominant among the currently commercial available synthetic biodegradable polymers are polyglycolic acid (PGA), polylactic acid (PLA), polylactic acid-glycolic acid copolymer (PLGA), poly-ε-caprolactone (PCL), and derivatives and copolymers thereof. Examples of natural biodegradable polymers used as scaffold materials include collagen, alginate, hyaluronic acid, gelatin, chitosan, and fibrin. The scaffold may be in various forms, such as sponges, gels, fibers, and microbeads, with the predominance of porous sponges and injectable hydrogel.
There are various technical problems with tissue engineering. Inter alia, the most urgent core technique in relation to scaffolds is to construct a cytocompatible surface environment. In light of the scaffol's intrinsic role of providing a three-dimensional environment advantageous for cell adhesion and growth, properties of scaffold's surface on which cell adhesion is made may be a decisive factor of current and future behaviors of the cells.
However, deficient basis studies on the use of cell scaffolds leads to the underdevelopment of cell scaffolds in human tissue-mimic three-dimensional structures, which, in turn, renders the application of cell scaffolds difficult.